Micrometastases or sub-micrometastases can be detected by standard histopathological method sometimes associated with immunohistochemistry in lymph nodes, bone marrowand blood. The consequence of these small size involvement may be prognostic and therapeutic. Two factors are necessary to assess this kind of involvement: the rate of involvement of non-sentinel lymph node after axillary lymph node dissection and significative difference of survivals. The rate of involvement of non-sentinel lymph node in case of micrometastases or sub-micrometastases is different from the rate of involvement in case of no lymph node metastases (7 to 8%) or in case of macrometases (30 to 50%). Micrometastase is an important factor to determine the rate of involvement of nonsentinel lymph node, the overall or disease free survival and to assess the need of radiotherapy and chemotherapy. In conclusion, micrometastases and sub-micrometastases have a clinical impact even if complementary axillary lymph node dissection is still discussed.
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